Method of improving the dimensional stability and elastic recovery of allcotton stretchable fabrics and products thereof



United States Patent METHOD OF IMPROVING THE DIlVIENSIONAL STABILITY ANDELASTIC RECOVERY OF ALL- COTTON STRETCHABLE FABRICS ANI) PROD- UCTSTHEREOF Albert S. Cooper, Jr., Metairie, Alton L. Murphy, New Orleans,and William G. Sloan and Wilson A. Reeves, Metairie, La, 'assiguors t0the United States of America as represented by the Secretary ofAgriculture No Drawing. Filed Dec. 14, 1962, Ser. No. 244,838

2 Claims. (Cl. 8-4163) A non-exclusive, irrevocable, royalty-freelicense in the invention herein described, throughout the world for allpurposes of the United States Government, with the power to grantsublicenses for such purposes, is hereby granted to the Government ofthe United States of America.

This invention relates to methods for improving the dimensionalstability and elastic recovery of all-cotton stretchable fabricsproduced by swelling type treatments. Stretch fabrics treated by themethods herein disclosed retain their original dimensions better whensubjected to such treatments as commercial and home laundering, and havemore rapid and complete recovery from stress or strain during normal usethan fabrics without subsequent treatment.

The improvements are obtained by reacting the cotton fibers withpolyfunctional reagents to crosslink the cellulose chains within thefiber to dimensionally stabilize the fiber and increase the recoveryforces necessary for the fiber to return to its original condition afterdeformation. This can be done with or without thermoplastic or othersoftening agents.

It is known that all-cotton stretch fabrics can be produced by shrinkingtechniques. The extent of the stretch properties imparted are directlyrelated to the extent of change that occurs in the cotton fibers whensubjected to a swelling type treatment. The most common swelling typetreatment used to impart stretch properties to cotton fabrics ismercerization in 13% to 45% aqueous solution of sodium hydroxide.Solution concentration is largely determined by the temperature of thetreating bath. Higher temperatures require higher solutionconcentrations for similar results. When the cotton fiber is permittedto shrink without restrictive tension in such a bath, the fiber shrinksfrom about 14% to 19%, depending on the fiber type and morphology. Sincethe density of the cotton fiber is reduced, the cross sectional area ofthe cotton fiber must increase slightly more than the amount oflongitudinal shrinkage that takes place. When cotton fibers are madeinto yarns the fibers are held together by lateral twist. When thefibers in cotton yarns are swollen as by rn'ercerization under relaxedconditions, the shrinkage of the fiber and the increase in crosssectional area have an additive effect to further reduce the length ofthe cotton yarns. This reduction in length of the cotton yarns variesfrom about 19% to 35% for yarns that do not develop crimp. It is knownthat cotton yarns spun with sufiiciently high twist have a tendency tocrimp. For any selected yarn the shrinking treatment causes an increasein the number of twist turns per inch. Consequently, for yarns of highertwist, additional reductions in length may be obtained by the formationof crimp in the yarn. Table I illustrates this effect of twist on theshrinkage of cotton yarns varying in twist multiplier (T.M.) from 2.5 to5.25

3,285,690 Patented Nov. 1 5, .1966

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TABLE I.EFFECT OF TWIST ON SHRINKAGE OF SLACK MERCERIZED 20/1 YARNST.M.: Percent shrinkage 2.50 32 3.25 41 4.00 53 4.75 62 5.25 67Equation:

Number of Turns Per Inch M Square Root of Yarn Number As can be seenfrom Table I, the length of a yarn can be reduced by more than by thecombined effects of fiber shrinkage, increase in cross sectional area ofthe fibers, and increase in twist due to shrinkage. Tests of higher T.M.were not made but indications are that further increases in T.M. wouldfurther increase the overall shrinkage of cotton yarns. This generalprinciple applies to any other cotton fiber swelling type treatment thathas essentially the same effects on the cotton fiber.

If the cotton yarns are woven into fabrics the amount of shrinkage, andconversely the amount of stretch, imparted are influenced by the weavingstructure. Fabrics of open weave would tend to shrink more because ofless restriction of crossing yarns, but be dependent on the yarn twist,and whether the weaving structure promoted or retarded the formation ofyarn crimp. Table II illustrates the variation in shrinkage obtained byrelaxed mercerization of plain weave fabrics that promotes yarn crimp.Thus the amount of shrinkage in cotton fabrics when subjected toswelling type treatment can be varied over very wide ranges by the wellknown principles of variations in yarn twist and fabric construction, toproduce stretchable cotton fabrics.

TABLE II.-SHRINKAGE OF FABRICS UPON SLACK MER- CERIZATION PercentShrinkage Fabric Description Warp Filling Regardless of the method .ofproducing stretchable cotton fabrics by swelling type treatments, thepermanence of the stretch properties and the quality of dimensionalstability are dependent on the permanence of the changes that took placein the cotton fiber. The permanence of the changes in the cotton fiberis related to the rearrangement of hydrogen bonds that hold thecellulose chains together within the cotton fiber. Hydrogen bonds areknown to be water sensitive, thus it is easier to rest-retch astretchable cotton fabric produced by a swelling type treatment while itis wet or exposed to high humidity than it is when the product is dry orexposed to a relatively low humidity.

To overcome this serious effect of moisture and to increase recoveryfrom deformation and dimensional stability it is necessary to supplementthe attractive forces of hydrogen bonding with co-valent cross-linksbetween cellulose chains. We have found that any polyfunctional reagentthat reacts with cotton cellulose to form co-valent cross-links betweencellulose chains will reduce the eifects of moisture on the stretchproperties of these products and also increase the rate and extent ofrecovery deformation as well as improve dimensional stability fortreatment such as laundering and tumble drying. Experiments have notbeen made to cover all such polyfunctional reagents, but as long as thereagent meets the requirements of being able to form co-valentcross-links between cellulose chains within the stretchable cotton fiberit would have essentially the same effect as the reagents tested. Alsovariations of cross-linking reagent application such as type ofcatalyst, treatment conditions, and the use of alkaline crystallizedreagents that may be applied as part of the swelling type treatment,would have essentially the same effect on the cotton fibers as moreconventional methods of application of the cross-linking reagents.

Although this invention was primarily for the improvement of thedimensional stability and elastic recovery for all-cotton stretchfabrics produced by swelling type treatments, it was found that thecrease recovery of these products was improved by the cross-linkingtreatments. Table III illustrates the improvement in crease recovery ofallcotton stretch fabrics produced by a swelling type treatment.

4 sodium hydroxide from the fabrics and rinsed thoroughly, and dried.

All processing steps were carried out under minimum processing tensionsto avoid restretching the fabric which would have the effect of reducingthe stretch properties. The fabrics were immersed in a solution of across-linking type reagent containing 7% dimethylolethylene urea, 1.5%polyethylene, and 3% magnesium chloride hexahydrate, and for conveniencepassed through squeeze rolls, to remove excess solution. However, themethod of applying the cross-linking reagent to the fabrics isunimportant, as long as it meets the requirements of the crosslinkingreagent being in molecular contact with the cotton cellulose and doesnot remove stretch properties. Techniques such as immersion andcentrifugal extraction, fogging, and jet spraying could also satisfythese requirements. The fabrics were dried at 190 F. for 4 minutes, thencured at 320 F. for 3 minutes to effect cross-linking. A processing washwas then given to remove extraneous materials from the treated stretchfabrics, and then dried. Again, minimum tensions are preferredprocessing conditions. The results of tests on stretch fabrics with andwithout cross-linking treatments are shown in Tables IV(A) and IV(B).

TABLE IV (A).PERCENT RECOVERY AFTER 70% OF TOTAL ELONGATION WarpDirection Filling Direction Sample Tested Immediate 5 Min. Perrna-Immediate 5 Min. Perma- Recovery Delay nent Set Recovery Delay nent Set80 x 54 Slack Mercerized Sheeting 2. 6 48. 0 49. 4 3. 7 40. 8 55. 5Resin Treated 80 x 54 Slack Mercerize Sheeting 7. 5 78.0 14. 5 4. 8 78 716. 5

Osnaburg Slack Mercerized 2. 8 32. 2 65. 0 2. 2 32. 5 65. 3

Resin Treated Osnaburg Slack erce 5. 9 69. 5 24. 6 3. 4 78. l 18. 5

Definitions: Percent of strain recovered as determined by the point ofintersection of a line drawn tangent to the slope of the unload curvewith the zero load axis.

5 minute delay is the percentage of the strain recovered after 5 minutesrelaxation of the strain on sample.

Permanent set is the percentage of the strain not recovered after the 5minute delay.

TABLE III.EFFECT 0F RESIN T R E A T M E N 'I' ON ggilAIsfisRECoVERYA-NGLE OF SLACK MERCERIZED These results show that easy care propertiescan be imparted to this type stretch fabrics similar to those impartedto conventional cotton fabrics by cross-linking type treatments.

Example 1 Cotton fabrics of the types used for household, industrial,and wearing apparel uses were swollen without restrictive tensions in a23% to 25% aqueous solution of sodium hydroxide at 25 C., for about 5minutes. Time of immersion varied with type of wetting agent used, thecondition of the fabric being treated, and the construction of thefabric. The immersion time should be long enough to insure essentiallycomplete fabric shrinkage. The shrunken fabrics were washed in hot waterup to 210 F. to facilitate removal of the sodium hydroxide. Highestpractical washing temperatures are preferred, but lower temperatureshave essentially the same effect. rics were then acid soured forcomplete removal of the The fab- Equation:

lR-l-Delayed Recovery+PS=% of Total Strain TABLE IV (B).INCREASE INLENGTH AFTER STRESSING TO ONE THIRD OF BREAKING LOAD NorE.Tl1e codedsamples are the same as those in Table IV (A), where IR represents theSlack Mercerized Sheeting which has been Resin Treated, and the 1 is itsControl, etc.

Definition: Growth is the percentage increase in the length of he testspecimen.

In every case comparing the slack mercerized and resin treated fabricswith the recovery values of the fabric that had been slack mercerizedonly, there was a significant improvement in the immediate elasticrecovery, the recovery after 5 minute relaxation, and a reduction in thepermanent set. Growth after cyclic loading to the breaking load isconsiderably less for the slack mercerized and resin treated fabrics incomparison with the fabric that has been slack mercerized only. Theseresults apply to both warp and filling tests.

The percent permanent set of slack mercerized-resin treated fabrics waslower at 40% than at 70% elongation, and even lower at 20% elongation.These changes are not linear but rather logarithmic, and the percentdifference between the 20%, 40%, and 70 samples, and their respectivecontrols also varies logarithmically, which simply means that ourinvention will impart excellent elasticity to,a cotton fabric with, ofcourse, better recovery when the treated fabric is not stretchedexcessively.

Example 2 A roll of fabric containing 100 yards of 80 x 80' cottonprintcloth was mercerized by the procedure described in Example 1 andtreated with an aqueous dimethylol ethyl carbamate solution. Themercerizing, as well as all other steps were carried out maintaining aminimum of restrictive tension on the cloth. The preparation andapplication of the resinous dimethylol ethyl carbamate on the cottonfabric were done on standard pilot plant equipment. Firstly, a 50%solution was prepared employing a 2:1 molar ratio of formaldehyde toethyl carbamate, respectively. The mixture consisted of 1432 grams ofethyl carbamate, 2940 grams of 36.3% formaldehyde, and 628 grams ofwater. This 5000 grams of solution was then brought to a pH of 8.5 with20% NaOH, and allowed to stand overnight, then adjusted to pH 7.0 withdilute HCl. Secondly, the solution was diluted to 10% total solids bythe addition of more water, which contained the 3% catalyst, 1.5%softener, and 0.1% wetting agent. Quantitatively these substances wereas follows:

Grams Magnesium chloride (6H O) 750 Polyethylene 1250 Wetting agent 50Water 17,950

Thirdly, this aqueous resin solution, which is 10 parts solids was thenapplied to the mercerized fabric, which was passed through squeezerolls, yielding a fabric with a homogenous 65% to 70% wet pickup. Thefabric was dried at 187 F., cured at 320 F., and washed and dried again.The drying and curing steps were carried out at 4 yards per minute, andthe last rinse took about 20 minutes. The final weight gain was ca. 5%.

Example 3 An 18 inch wide by yards long sample of 80 x 80 cottonprintcloth was slack mercerized in the same manner as the cloth ofExamples 1 and 2; then padded with a cross-linking resinous aqueoussolution, which was parts by weight tris-aziridinyl phosphine oxide. Thefabric was passed through squeeze rolls, and a wet pickup of 70% wasobtained. The pilot plant equipment was adjusted in such manner as tomaintain a minimum of restrictive tension on the fabric throughout theentire sequence of treatments.

The fabric was then passed through a roller-type, forced draft, gasfired oven to dry at 85 C. for about 4 minutes (actually 4 yards perminute) and cured immediately thereafter, in a tandem operation, at 155C. for about 4 minutes; washed in hot water for 30 minutes; and thendried on the tenter frame at 85 C. The resin add-on was about 8%.

The polyfunctional aqueous chemical mixture applied to the slackmercerized cloth was computed to obtain a 2000 gram quantity of a 15%tris-aziridinyl phosphine oxide (APO) solution, and was prepared bymixing the following quantities, immediately prior to the use of thesolution, and at temperatures of to to avoid pre- We claim:

1. A process for the production of a dimensionally stabilizedcreaseproof, and stretchable cotton fabric comprising (a) Slackmercerizing a cotton fabric with an aqueous solution containing aboutfrom 13 to 45 parts by weight of sodium hydroxide to produce anessentially completely-shrunken cotton fabric;

(b) hot water-washing and acid-souring the thus shrunken cotton fabricto remove all excess sodium hydroxide;

(c) resin-treating the shrunken cotton fabric, under minimum processingtensions to avoid restretching the shrunken cotton fabric and to awet-pickup of about from 60 to weight percent, with an aqueous solutioncontaining about from 0.7 to 3.0 weight percent of an acid-type catalystand about from 5 to 15 weight percent of dimethylol ethylene urea; and

(d) while maintaining said minimum processing tensions to avoidrestretching the shrunken cotton fabric, heating the resin-treatedshrunken fabric at a temperature of about from 25 to C. for about from15 minutes to 3 minutes, the longer times being employed with the lowertemperatures, to dry cure the dimethylol ethylene urea, thereby toproduce a dimensionally stabilized, creaseproof, and stretchable cottonfabric.

2. The dimensionally stabilized, creaseproof, and stretchable cottonfabric produced by the process of claim 1.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS607,582 9/1948 Great Britain. 727,890 4/ 1955 Great Britain. 825,60812/1959 Great Britain.

OTHER REFERENCES American Dyestutf Reporter, October 31, 1961, pages(P849) 37 to (P853) 41.

Goldthwait et al., Textile Research Journal, January 1955, pages 4757.

Marsh, John T: An Introduction to Textile Finishing, Second Impression,1948, pages 253-256, 390-400, Chapman and Hall Ltd., London, England.

Mercerising, John T. Marsh, 1942, pages 179-184, D. Van Nostrand Co.,Inc., New York, New York.

NORMAN G. TORCHIN, Primary Examiner.

J. TRAVIS BROWN, Examiner.

H. WOLMAN, Assistant Examiner.

1. A PROCESS FOR THE PRODUCTION OF A DIMENSIONALLY STABILIZINGCREASPROOF, AND STRETCHABLE COTTOM FABRIC COMPRISING (A) SLACKMERCERIZING A COTTON FABRIC WITH A AQUEOUS SOLUTION CONTAINING ABOUTFROM 13 TO 45 PARTS BY WEIGHT OF SODIUM HYDROXIDE TO PRODUCE ANESSENTIALLY COMPLETELY-SHRUNKEN COTTOM FABRIC; (B) HOT WATER-WASHING ANDACID-SOURING THE THUSSHRUNKEN COTTON FABRIC TO REMOVE ALL EXCESS SODIUMHYDROXIDE; (C) RESIN-TREATING THE SHRUNK COOTTON FABRIC, UNDER MINIMUMPROCESSING TENSIONS TO AVOID RESTRECTING THE SHRUNKEN COTTON FABRIC ANDTO A WET-PICKUP OF ABOUT FROM 60 TO 100 WEIGHT PERCENT, WITH AN AQUEOUSSOLUTION CONTAINING ABOUT FROM 0.7 TO 3.0 WEIGHT PERCENT OF AN ACID-TYPECAYALYST AND ABOUT FROM 5 TO 15 WEIGHT PERCENT OF DIMETHYLOL ETHYLENEUREA; AND (D) WHILE MAINTAINING SAID MINIMUM PROCESSING TENSIONS TOAVOID RESTRETCHING THE SHRUNKEN COTTON FABRIC, HEATING THE RESIN-TREATEDSHRUNKED FABRIC AT A TEMPERATURE OF ABOUT FROM 25* TO 160*C. FOOR ABOUTFROM 15 MINUTES TO 3 MINUTES, THE LONGER TIMES BEING EMPLOYED WITH THELOWER TEMPERATURES, TO DRY CURE THE DIMETHYLOL ETHYLENE UREA, THEREBY TOPRODUCE A DIMENSIONALLY STABILIZED, CREASPROOOF, AND STRETCH ABLE COTTONFABRIC.